Bipolar Power Transistor Tester h21E
Here you will find our development for a bipolar power transistor tester. It measures the short-circuit forward current ratio \((\frac{I_{out}}{I_{in}}) @(V_{out}=0)\) commonly known as \(h_{21E}\).
Gallery
Schematics
Bipolar Power Transistor Tester h21E
( as PDF)
Bipolar Power Transistor Tester h21E PCB
( as PDF) ( as LAY)
Description
We built this handy device because we know the frustration of dealing with mismatched transistors in audio builds. Whether you’re working on a push-pull amplifier or just need parallel transistors, getting them matched is crucial for great sound quality and reliable operation.
We’ve created a simple but effective solution! Our design works like a specialized current generator that measures the base current of power transistors. We made it compatible with both NPN and PNP types, so you can test any power transistor you have. Just connect your transistor, read the milliammeter, and you’ll know its \(h_{21E}\) (current gain) value. Group the ones with similar readings, and you’re all set for your audio project!
We designed our prototype using a 100 \(\mu A\) milliammeter with 1000 \(\Omega\) internal resistance. Don’t have the same meter? No problem! We’ve made sure you can adapt the design - just recalculate resistors R3 through R8 to match your meter’s specs. We kept the whole thing straightforward and used easily available components.
What we use it for:
- Building our high-quality audio amplifiers
- Upgrading older audio equipment
- Testing transistor batches
- Ensuring consistent sound quality in our projects
We’ve been using this in our workshop for years, and it’s become an essential tool for all our audio builds. Give it a try - we think you’ll find it just as useful as we do!
Good Luck!